1. Field of the Disclosure
This application relates generally to the surface mount of electronic components onto a printed circuit board by employing a reflow process, and more particularly to a reflow soldering oven that is designed to heat the printed circuit board during the reflow process.
2. Discussion of Related Art
In the fabrication of printed circuit boards, electronic components are often surface mounted to a bare board by a process known as “reflow soldering.” In a typical reflow soldering process, a pattern of solder paste is deposited onto the circuit board, and the leads of one or more electronic component are inserted into the deposited solder paste. The circuit board is then passed through an oven where the solder paste is reflowed (i.e., heated to a melt or reflow temperature) in the heated zones and then cooled in a cooling zone to electrically and mechanically connect the leads of the electronic component to the circuit board. The term “circuit board” or “printed circuit board,” as used herein, includes any type of substrate assembly of electronic components, including, for example, wafer substrates.
As stated above, present day reflow ovens have heating and cooling chambers. To achieve a consistent reflow process profile, flux needs to be extracted and collected away from the heating/cooling chambers. To achieve flux removal, there are two types of reflow ovens—air reflow ovens and inert atmosphere reflow ovens. With the air reflow ovens, flux is extracted by an exhaust system. With the inert atmosphere reflow ovens, a flux management system is used to extract flux from the heating/cooling chambers.
Both flux removal systems suffer from well-known shortcomings. With both systems, flux continues to deposit onto the inner walls of the heating/cooling chambers. Over time, the flux collected on the chamber walls create problems during production as excess flux may drip back onto actual production printed circuit boards, thereby potentially contaminating or otherwise compromising the attachment of components onto the printed circuit boards.
With current production requirements, it is desired to continuously operate fabrication equipment, including reflow ovens. Thus, when contemplating scheduled maintenance of the fabrication equipment, it is further desirable to keep down-time as short as possible. During such scheduled maintenance, the removal of flux on chamber walls is generally not addressed. Thus, ongoing flux contamination exposed to the printed circuit boards being produced would remain. Over time, excess flux may also cause premature failures of components of the reflow oven, including blowers designed to facilitate air circulation within the reflow oven chamber.